Psychology
2013. Vol.4, No.8, 669-675
Published Online August 2013 in SciRes (http://www.scirp.org/journal/psych) http://dx.doi.org/10.4236/psych.2013.48095
Autonomic Mechanisms of Emotional Reactivity and Regulation
Catherine C. Uy1, Iain A. Jeffrey2, Matthew Wilson3, Viswanath Aluru1,
Anita Madan4, Ying Lu5, Preeti Raghavan1,5*
1Department of Rehabilitation Medicine, New York University School of Medicine, New York, USA
2Touro College of Osteopathic Medicine, New York, USA
3Hunter College, New York, USA
4Department of Psychiatry, New York University School of Medicine, New York, USA
5Education and Human Development, Steinhardt School of Culture, New York University, New York, USA
Received May 15th, 2013; revised June 29th, 2013; accepted July 23rd, 2013
Copyright © 2013 Catherine C. Uy et al. This is an open access article distributed under the Creative Commons
Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the
original work is properly cited.
The ability to perceive and regulate our emotions appropriately is essential for social behavior. Our sub-
jective emotional states to changing external cues are accompanied by physiological changes in heart rate
variability (HRV), which is regulated by the sympathetic and parasympathetic branches of the autonomic
nervous systems (ANS). In this pilot study, we sought to elucidate the autonomic basis of emotional reac-
tivity and regulation in response to ecologically-valid emotional stimuli—presented in the form of film-
clips—in healthy subjects. Subjects watched a series of videos, validated to elicit feelings of amusement,
sexual amusement, sadness, fear, and disgust. Subjects were also asked to regulate the outward expression
of their response to disgust by suppressing or amplifying it when instructed. Electrodes placed on the
torso measured cardiac and respiratory signals, which were processed to compute HRV, which when ana-
lyzed with the concurrent respiratory signal calculates measures of parasympathetic activity (RFA, Res-
piratory Frequency Area, from higher frequencies) and sympathetic activity (LFA, Low Frequency Area,
from lower frequencies). Fluctuations in LFA and RFA were computed by the coefficient of variation,
and the intensity of the emotional response to the film-clips was captured via questionnaires. Our results
suggest that in healthy individuals, higher intensities of subjective emotional experience, both positive
(e.g., amusement) and negative (e.g., amplified disgust) elicit higher LFA (sympathetic) responses,
whereas emotional regulation is mediated primarily by fluctuations in RFA (parasympathetic) activity.
Furthermore, correlations between emotional intensity and components of HRV suggest that higher posi-
tive or lower negative emotional states may increase the capacity for emotional regulation via modulation
of the parasympathetic component. Our results suggest that a sense of humor might facilitate emotional
control.
Keywords: Heart Rate Variability; Sympathetic; Parasympathetic; Emotions
Introduction
Emotional perception and regulation inform the way we react
to different situations, both in terms of how we feel inside and
how we present ourselves to others. To form relationships and
behave according to social norms we need to regulate our feel-
ings based on ever-changing external cues. Based on these cues,
we must decide quickly if our feelings are appropriate to the
specific situation and adapt our behavior accordingly (Izard,
Fine et al., 2001). In many conditions, such as traumatic brain
injury (Thurman, Alverson et al., 1999; Bornhofen & McDonald,
2008; McDonald, Bornhofen et al., 2009; de Sousa, McDonald
et al., 2012; Hammond, Davis et al., 2012), post-traumatic stress
disorder (Aupperle, Allard et al. 2012), and autism (Bal, Har-
den et al., 2010), this ability is impaired leading to overreaction
or inappropriate behavior. A basic understanding of how healthy
individuals perceive, react to, and regulate their response to
various emotions is first necessary before we can begin to de-
termine how these processes may differ in those with emotional
dysfunction and dysregulation.
When we feel an emotion, our subjective emotional experi-
ences are accompanied by measurable physiological changes in
heart rate, skin conductance and respiratory rate (Zuckerman,
Klorman et al., 1981; Gross & Levenson, 1993; Gross & Le-
venson, 1997). These parameters measure arousal, reflecting
activity of the autonomic nervous system (ANS), but do not
differentiate between activity of the sympathetic and parasym-
pathetic branches of the ANS. According to Porges’ polyvagal
theory, parasympathetic influence on the heart allows one to
adjust metabolic output to optimize social interactions; in con-
trast, sympathetic activity is necessary for mobilization during
threatening situations (Porges, 1995; Porges, 2007). While both
branches influence heart rate, they do so by different mecha-
nisms which are activated by specific environmental circum-
stances. For example, an increase in heart rate in response to a
fearful stimulus may, in some cases, be a result of sympathetic
activation, while in others may arise from parasympathetic
*Corresponding author.

C. C. UY ET AL.
withdrawal (Stifter, Dollar et al., 2011). Therefore, to better
understand the autonomic mechanisms of emotional reactivity
and regulation, it would be prudent to study activity patterns of
both the sympathetic and parasympathetic branches of the ANS
and examine how they interact in response to distinct affective
stimuli.
Sympathetic and parasympathetic output is thought to be
regulated by the brain’s central autonomic network (CAN)
(Benarroch, 1993), which includes regions of the cortex, brain-
stem and limbic systems, and is involved in a wide range of
processes from homeostasis to goal-directed behavior (Appel-
hans & Luecken, 2008). By integrating information about the
external environment with that of the body’s internal physio-
logical state, the CAN modulates activity of the sympathetic
and parasympathetic branches of the nervous system to influ-
ence heart rate. Sympathetic signals influence the sinoatrial
node via the neurotransmitter norepinephrine to gradually in-
crease heart rate, achieving peak effect after 4 seconds and
returning to baseline after 20 seconds. In contrast, parasympa-
thetic signaling via acetylcholine slows heart rate with a short
response latency, achieving peak effect after 0.5 seconds and
returning to baseline within 1 second (Bazhenova, Plonskaia et
al., 2001; Pumprla, Howorka et al., 2002). The frequency spec-
trum of heart rate variability (HRV) thus reflects sympathetic
and parasympathetic influences on heart rate (Appelhans &
Luecken, 2006). HRV, when analyzed concurrently with the
respiratory signal calculates measures of parasympathetic activ-
ity (RFA, Respiratory Frequency Area, from higher frequencies)
and sympathetic activity (LFA, Low Frequency Area, from
lower frequencies) (Akselrod, Gordon et al., 1981; Aysin &
Aysin, 2006).
The goal of this study is to elucidate the autonomic mecha-
nisms of emotional reactivity and regulation in response to
ecologically-valid affective stimuli. We used film clips vali-
dated to elicit specific emotional responses (Rottenberg, Ray et
al., 2007; Schaefer, Nils et al., 2010) and measured the fre-
quency spectra of HRV and respiratory activity when partici-
pants watched the videos.
Methods
Subjects
Seven healthy subjects, ranging in age from 23 to 40 years
(mean ± SD = 29.8 ± 6.2 years), with no history of psychiatric
disease or complicating medical problems, such as uncontrolled
hypertension, diabetes, neurological illness such as stroke, epi-
lepsy, or demyelinating disease participated in the study. Four
of the subjects were female [57%].
Procedure
After obtaining informed consent, subjects were seated at a
table, in front of a computer monitor, in a well-lit, 11' × 23'
room. Three electrodes, one placed below each clavicle and one
on the left lower ribcage, measured electrocardiographic and
respiratory signals (ANSAR Medical Technologies, 2005).
First, a baseline electrocardiographic recording was obtained
with no video stimulus. Subjects were instructed to look for-
ward, relax, and breathe normally for 2 minutes.
Subjects were then told that they were going to watch a se-
ries of eight video clips (2 - 5 minutes long) (Table 1). Each
subject was randomly assigned to watch one of two sets of
Table 1.
Summary of the emotion-eliciting film stimuli.
Target
emotion Movie title & description Time (min)
Neutral
Sticks—Different colored sticks gradually
accumulate on a black background
(non-commercial screen saver, soundless). 4.6
Amusement Something About Mary—A man fights with a
small dog. 4.33
Sadness City of Angels—The aftermath of a woman on a
bike hit by a truck and dying in a man’s arms. 4.35
Sexual
amusement
When Harry M et Sally—A woman loudly
simulates an orgasm in a crowded diner. 3.75
Fear The Shining— A boy plays alone in an empty
hallway. 2.5
Trainspotting—A man defecates then dives into
a filthy toilet. 2.38
Amputation—noncommercial recording of an
arm amputation. 2.3
Video set 1
Disgust
Bad Taste—A group of young men eat vomit. 2.96
Neutral
Sticks—Different colored sticks accumulate
gradually on a black background (screen saver,
soundless). 4.6
Amusement Benny and Joon—A man fools around in a
diner. 3.33
Sadness The Champ—A young boy grieves over his
dying father. 3.83
Sexual
amusement
A Fish Calle d Wanda—A woman is sexually
aroused while her male companion is found
naked by the owners of the house they are in. 4.08
Fear
Silence of the Lambs—A woman chases a
dangerous man at gunpoint and comes across a
corpse in a bathtub. 4.6
Vampire’s Kiss—A man eats a cockroach. 1.65
Black Swan—A woman peels back a hangnail.1.87
Video set 2
Disgust
Pink Flamingoes—A woman eats dog feces. 2.5
videos, validated to elicit the same target emotions. Each clip
began with 10 seconds of written instructions, stating “Please
relax and watch the +”, followed by 60 seconds of a white +
sign on a black background. This was provided to bring the
subjects back to baseline prior to each film-clip, which would
then automatically start playing. Subjects were not informed of
the sequence of the film clips. After watching each video, sub-
jects completed a post-film questionnaire to assess the intensity
of their emotional response to the film clip.
Module 1: Positive and Negative Affect. Subjects watched
five short video clips targeting the following emotions: neutral,
amusement, sadness, sexual amusement, and fear. The order of
the clips was the same across all subjects and was chosen to
counter-balance positively- and negatively-valenced affective
stimuli, to prevent subjects from being overwhelmed in either
direction. Before each video, subjects were told, “We will now
be showing you a short film clip. It is important to us that you
watch the film clip carefully.”
Module 2: Disgust Regulation. Subjects watched three dif-
ferent video clips validated to elicit a disgust response. For the
first video, subjects just watched the film clip while their reac-
tivity was measured as in module 1 (unregulated response). For
the second video, subjects were instructed to suppress their
reactions. They were told, “Watch the film clip carefully. If you
have any feelings as you watch the film, please try your best
not to let those feelings show.” For the third video, subjects
were instructed to amplify their reactions. They were told,
670

C. C. UY ET AL.
“Watch the film clip carefully. If you have any feelings as you
watch the film clip, try your best to let those feeli ngs show.”
Apparatus
Physiological Measurements. Electrocardiographic and res-
piratory signals were sampled at 250 Hz and 50 Hz, respec-
tively and collected using ANSAR ANX 3.0 software (ANSAR
Medical Technologies, Inc., Philadelphia, PA). Heart rate vari-
ability (HRV) was computed every 0.25 seconds and time-
frequency spectral analysis was performed to quantify ANS
activity. The respiratory frequency area (RFA) measured para-
sympathetic activity from higher frequency areas of the HRV
spectrum as determined from time-frequency analyses of respi-
ratory activity (Aysin & Aysin, 2006). RFA represents the fre-
quency ranges associated with Respiratory Sinus Arrhythmia,
known to be a cardio-vagal response, reflecting parasympa-
thetic activity (Akselrod, Gordon et al., 1981; Appelhans &
Luecken, 2008). Low frequency area (LFA) is defined as the
area under the heart rate spectral curve over the frequency
range from 0.04 - 0.10 Hz, or the lower limit of RFA range
(ANSAR Medical Technologies, 2005; Colombo, Shoemaker et
al., 2008). By localizing and omitting the parasympathetic in-
fluence (e.g., from Respiratory Sinus Arrhythmia) from the low
frequency range of HRV, LFA primarily corresponds to activity
from the sympathetic nervous system (Aysin & Aysin, 2006;
Colombo, Shoemaker et al., 2008).
Self-Reported Emotional Responses. After each film clip,
subjects completed a short post-film questionnaire to rate the
intensity of their feelings of amusement, anger, anxiety, confu-
sion, contempt, disgust, embarrassment, fear, guilt, happiness,
interest, joy, love, pride, sadness, shame, surprise and unhappy-
ness on a scale of 0 (none) to 8 (extreme). They were also asked
to indicate if they had seen the film clip prior to the study
(Rottenberg, Ray et al., 2007).
Data Reduction and Statistical Analyses
For the purposes of this study, we focused on the interval of
interest (IOI)—the 30 seconds of the film clip that most
strongly elicited the target emotion. Therefore, all data analysis
pertains to ANSAR recordings during the IOI of each film clip.
LFA and RFA values for time points at which RFA  0.1 bpm2
were dropped, as they are un-interpretable for healthy subjects.
For each target emotion, we measured 1) the mean LFA and
RFA activity, 2) the geometric mean of the ratio between LFA
and RFA (LFA/RFA) that quantifies their interrelationship, and
3) the coefficient of variability of both LFA and RFA that
quantifies the fluctuation in LFA and RFA independent of the
mean level.
A linear mixed effect model was used to examine how the
activity levels, interrelationship and variability in LFA and
RFA change across different target emotions. A random effect
at subject level was used to control for individual heterogeneity.
Statistical software package R 2.15.2 was used and package
lmer was used to fit the model. To respect the normality as-
sumption, a logarithm transformation was done to the geomet-
ric mean of the ratio of LFA over RFA. The results based on
this particular model were then converted into multiplicative
effects at the original scale. Relationships between self-reported
emotional responses and autonomic parameters were examined
using Spearman Rank correlations. Three levels of statistical
significance (1%, 5% and 10%) are reported.
Results
Positive Affective Stimuli Increase LFA and
Fluctuation in RFA
Physiology. Figure 1(a) shows mean LFA and RFA values
during the IOI across all subjects. Compared to neutral, mean
LFA increased significantly during both amusement (mean
difference (md) = 12.42, p < 0.01) and sexual amusement (md
= 6.08, p < 0.05). There were no statistical differences in mean
RFA across any of the stimuli compared to neutral. The mean
LFA was significantly higher than the mean RFA only during
amusement (md = 10.25, p < 0.01).
At the subject level, the ratio between LFA and RFA (Figure
1(b)) for the neutral stimulus was close to 1 (LFA/RFA = 0.91),
suggesting that LFA and RFA were well balanced. For both
positively-valenced stimuli, the LFA/RFA ratios were signifi-
cantly higher than for the neutral or the negatively-valenced
stimuli (LFA/RFA amusement = 4.84, p < 0.01; sexual amuse-
ment = 2.53, p < 0.05), suggesting that positively-valenced
stimuli elicited greater autonomic activity in the lower fre-
quency bandwidth of HRV.
The coefficient of variation of LFA (cvLFA) was relatively
constant across all affective stimuli (Figure 1(c)). Only the
cvRFA for amusement was significantly higher than that for
neutral (md = 0.26, p < 0.01). In addition, the difference be-
tween the cvRFA and cvLFA was significant during amuse-
ment (md = 0.47, p < 0.01) and fear (md = 0.314, p < 0.05).
Note however that 4 out of 7 subjects had seen the fear-pro-
voking film clip previously.
Subjective experience. To confirm that the film clips were
eliciting the intended target emotion, we examined the intensity
of the various emotions elicited by the film-clips on the post-
film questionnaire (Figure 1(d)). Note that the emotions that
were felt most intensely for each film clip corresponded with
the target emotion for that clip. Sexual amusement provoked
some embarrassment while non-sexual amusement did not.
There was also a strong correlation between reported embar-
rassment and the cvRFA (r = 0.971, p < 0.01), suggesting that
those who experienced more embarrassment showed greater
fluctuation in the higher frequency component of HRV. Inter-
estingly, there was a negative correlation between self-reported
fear and both mean LFA (r = −0.564, p = 0.18) and mean RFA
(r = −0.873, p < 0.01).
Regulation of Disgust Is A ssociated wit h Fluctu at ions
in RFA
Physiology. Figure 2(a) shows the mean LFA and RFA dur-
ing unregulated and regulated disgust film-clips compared to
neutral. The mean LFA during disgust amplification was sig-
nificantly higher compared to neutral (md = 13.125, p < 0.01),
unregulated disgust (md = 10.366, p < 0.01) and disgust sup-
pression (md = 10.043, p < 0.01). The difference between mean
LFA and RFA during disgust amplification was also significant
(md = 18.21, p < 0.05). No significant differences were found
in mean RFA across the stimuli. The ratio of LFA/RFA was
higher during unregulated disgust (LFA/RFA = 2.39, p < 0.10)
and disgust amplification (LFA/RFA = 2.66, p < 0.05) com-
pared to neutral and disgust suppression (Figure 2(b)). Inter-
estingly, LFA/RFA ratios during disgust suppression ap-

C. C. UY ET AL.
672
Figure 1.
Emotional reactivity in response to positively-valenced and negatively-valenced film stimuli. The symbols indicate statistical signifi-
cance compared to the neutral stimulus: ‡p < 0.01, *p < 0.05. (a) Mean LFA and RFA levels; (b) Mean ratio of LFA to RFA
(LFA/RFA); (c) Coefficient of variation of LFA and RFA; (d) Self-reported emotional intensity scores for various emotions elicited by
the film-clip on the post-film questionnaire (PFQ). In sexual amusement, EMB = embarrassment. In sadness, INTER = interest.
Discussion
proached that of the neutral stimulus, suggesting that healthy
subjects were indeed able to regulate their autonomic activity
when prompted to do so. The cvRFA was significantly higher
than the cvLFA during disgust suppression (md = 0.31, p <
0.05) and amplification (md = 0.31, p < 0.05) (Figure 2(c)),
suggesting that emotional regulation is reflected in increased
higher frequency HRV fluctuations.
In this study, we measured autonomic activity as reflected in
the frequency spectrum of HRV, modulated by respiratory ac-
tivity, when healthy subjects watched a series of film clips,
which were validated to elicit specific target emotions. Our data
suggest that in healthy individuals, emotional reactivity or
arousal is reflected in the mean level of activity in the Low
Frequency Area (LFA), a measure of sympathetic activity,
whereas emotional regulation is reflected in fluctuations of the
Respiratory Frequency Area (RFA), a measure of parasympa-
thetic activity.
Subjective experience. Although disgust, surprise and anxiety
were experienced with all three disgust-inducing film clips, the
intensity of these emotions varied during suppression and am-
plification (Figure 2(d)). Disgust suppression was associated
with less intense feelings of disgust compared with disgust am-
plification (md = 1.85 units, p < 0.1), but greater anxiety (md =
3 units, p < 0.05). Interestingly, the intensity of anxiety during
disgust suppression was negatively correlated with the cvRFA
(r = −0.927, p < 0.01), suggesting that those who experienced
less anxiety showed greater fluctuation in the higher frequency
component of HRV. In contrast, during amplification, anxiety
was positively correlated with cvRFA (r = 0.778, p < 0.05),
suggesting that those with more anxiety showed greater cvRFA,
which is consistent with the direction of regulation. In addition,
a strong positive correlation was noted between the intensity of
amusement and cvRFA during disgust suppression (r = 0.082, p
< 0.05), suggesting that individuals who experienced higher
intensity of amusement also showed greater fluctuation in the
higher frequency component of HRV.
Both processes may occur simultaneously depending on the
emotional cues, suggesting a complex interplay between sym-
pathetic and parasympathetic mechanisms in response to chang-
ing environmental cues. Furthermore, correlations between self-
reported emotional intensity and components of HRV suggest
that higher positive or lower negative emotional states may
increase the capacity for emotional regulation.
Autonomic Basis of Emotional Reactivity
In our study, subjects responded to positively-valenced amus-
ing stimuli with relatively high mean LFA, and high LFA/RFA
ratios compared to neutral; these emotions also evoked intense
subjective feelings. Increased autonomic activity when one is
amused may be due to expressive behavior such as laughing,

C. C. UY ET AL.
Figure 2.
Emotional reactivity and regulation in response to disgust-inducing stimuli. The symbols indicate statistical significance
compared to the neutral stimulus unless indicated otherwise: ‡p < 0.01, *p < 0.05, +p < 0.1. (a) Mean LFA and RFA levels; (b)
Mean ratio of LFA to RFA (LFA/RFA); (c) Coefficient of variation of LFA and RFA; (d) Self-reported emotional intensity
scores on the post-film questionnaire (PFQ). Note comparisons in intensity of disgust and anxiety between disgust suppres-
sion and amplification.
which has been shown to increase arousal, even after control-
ling for somatic activity (Sakuragi, Sugiyama et al., 2002; Giu-
liani, McRae et al., 2008). However, a meta-analysis of the li-
terature on autonomic activity with induced amusement (Shiota,
Neufeld et al., 2011) shows mixed results: in some studies
amusement produced little or no increase in autonomic arousal
relative to negative emotions (Levenson, Ekman et al., 1992),
while others show reduced (Fredrickson & Levenson, 1998;
Fredrickson, Mancuso et al., 2000) or increased arousal (Neu-
mann & Waldstein, 2001; Mauss, Levenson et al., 2005;
Giuliani, McRae et al., 2008). Some of these discrepancies may
be accounted for by methodological differences. However, in
our study, during the sexual amusement film clips, subjects also
reported feelings of embarrassment and mild anxiety, which
have been shown to decrease arousal (Gerlach, Wilhelm et al.,
2003). Consequently, the increase in LFA was not as pro-
nounced with the sexual amusement film clips as observed with
the non-sexual amusement clips.
Furthermore, negatively-valenced stimuli (sadness and fear)
did not elicit high LFA or LFA/RFA ratios in our study, and the
subjects did not perceive the negative stimuli as intensely as the
positive stimuli either. Both decreased sympathetic arousal and
low LFA/RFA ratios have been noted in grief states (Sternbach,
1962; Sakuragi, Sugiyama et al., 2002), typically characterized
by a flat affect. However, our results contradict other studies,
which suggest that negative emotions lead to increased sympa-
thetic activity (Fredrickson & Levenson, 1998; Fredrickson,
Mancuso et al., 2000). Some of these differences may be due to
the fact that traditional HRV measures may not account for
Respiratory Sinus Arrhythmia (and thus parasympathetic activ-
ity) within the low frequency range of HRV, which is sub-
tracted out to compute the LFA with the present technology
(Aysin & Aysin, 2006). We did observe an increase in the mean
LFA and high LFA/RFA ratios during disgust, particularly
when subjects were asked to amplify their expression of disgust.
In contrast, fear-provoking stimuli, which might be expected to
produce high arousal and parasympathetic withdrawal (Bernt-
son, Cacioppo et al., 1991), did not lead to a statistically sig-
nificant difference in LFA and LFA/RFA ratio compared to the
neutral stimulus. Instead, surprisingly, mean LFA was nega-
tively correlated with the intensity of fear reported. Our unusual
results may be explained by the finding that 4/7 subjects had
seen the fear-inducing film clip previously. It is possible that
prior memory of the film and knowledge of what is going to
happen next attenuated the emotional impact of the clip. Fur-
thermore, fear elicited lower mean RFA, but higher fluctuations
in RFA as seen with the amusement film clip, suggesting that
parasympathetic regulatory mechanisms (see below) may have
been activated. Our sample size is too small to directly relate
subjective emotional intensity to autonomic reactivity. Never-
theless, taken together, our results suggest that in healthy indi-
viduals, higher intensities of subjective emotional experience,
both positive (e.g., amusement) and negative (e.g., amplified
disgust) elicit higher responses in the lower frequency band-
width (LFA) of HRV. The mean LFA and LFA/RFA ratios
may therefore provide an objective measure of the intensity of

C. C. UY ET AL.
feelings.
Autonomic Basis of Emotional Regulation
In order to evaluate emotional regulation, we focused on the
response to disgust-inducing stimuli. Disgust is a primal, uni-
versal emotion that may be less prone to external influences or
personal preferences compared with other emotions such as
amusement or sadness. In our study, subjects always started
with the unregulated disgust condition, which elicited subjects’
natural response to disgust. We then asked subjects to suppress
their disgust; and finally, we asked them to amplify their re-
sponse to disgust. We believe that this order of stimulus pres-
entation would override any desensitization that may occur
from repeated exposure to disgust-inducing stimuli. Note that
three different disgust film-clips were used for the three condi-
tions.
Unregulated disgust elicited higher mean LFA and LFA/RFA
ratios compared with the neutral film clip; however, the differ-
ence only showed a trend toward significance, perhaps due to
our small sample size. The self-report questionnaire indicated
that disgust was strongly elicited. Previous studies have noted
increased arousal in response to disgust-eliciting film stimuli
(Gross & Levenson, 1993). In contrast, when asked to suppress
their disgust, subjects balanced their LFA and RFA and the
LFA/RFA ratio approached that of the neutral stimulus. In ad-
dition, the intensity of disgust was reduced on the post-film
questionnaire, suggesting that subjects were indeed able to
suppress their feelings of disgust. The reaction to disgust was
also clearly exaggerated with instructions to amplify. The mean
LFA, difference between mean LFA and RFA, and LFA/RFA
ratio were also higher with disgust amplification. Our data are
consistent with previous studies, which found that exaggerating
expressive behavior results in higher sympathetic arousal, even
on non-somatic measures (Zuckerman, Klorman et al., 1981).
Thus healthy subjects can clearly regulate both autonomic
arousal, reflected in the mean level of the LFA, and subjective
emotional responses when requested to do so.
Interestingly, both disgust suppression and amplification led
to increased fluctuation in the RFA, indicating higher levels of
parasympathetic activation during emotional regulation. This
pattern is similar to that observed during amusement and fear
film-clips, which also appeared to activate regulatory mecha-
nisms (see above). Parasympathetic activation corresponds with
a sense of calm (Fredrickson & Levenson, 1998) and higher at-
tention (Healy, 2010) which may be needed during regulation.
We also noted a strong positive correlation between fluctuation
in RFA (cvRFA) and intensity of amusement, and a strong
negative correlation with anxiety during disgust suppression.
These results suggest that higher positive or lower negative
emotional states may increase the capacity for emotional regu-
lation, and lend support to the theory of vagal tone as a physi-
ologic index of stress (Porges, 1995). Interestingly, anxiety lev-
els were greater during disgust suppression than during disgust
amplification. Decreased anxiety during amplification may cor-
respond with subjects’ ability to give an unrestrained, exagger-
ated reaction, while increased anxiety with suppression may re-
sult from the stress of not being able to express one’s feelings.
Taken together, our results suggest that emotional regulation is
mediated by parasympathetic activation resulting in fluctuations
in the RFA, and that higher positive or lower negative emo-
tional states may enhance the capacity for emotional regulation.
Conclusion and Future D i r ections
Despite the small sample size, this study leads to a number of
important findings: 1) Emotional reactivity or arousal is medi-
ated by increase in the mean level of the lower frequency com-
ponent of HRV, or LFA, which measures sympathetic activity;
2) the mean LFA and LFA/RFA ratio provide an objective
measure of the subjective intensity of one’s feelings whether
positive or negative; 3) Moment to moment fluctuations in
respiratory activity modulated HRV frequency, or RFA, reflects
parasympathetic-discharge-mediated emotional regulation; and
4) Positive subjective feelings appear to enhance the capacity
for emotional regulation. These findings provide insight into
mechanisms by which we react to and regulate our emotions to
changing environmental cues, and form the basis for future
research in conditions characterized by emotional dysfunction
such as traumatic brain injury, post-traumatic stress disorder,
and autism.
Acknowledgements
This project was funded by pilot grant from the Rusk Insti-
tute of Rehabilitation Medicine, New York University School
of Medicine. We are grateful for support to IJ through the Re-
habilitation Research Experience for Medical Students (RREMS)
program sponsored by the Association of Academic Physiatrists
and the Foundation for Physical Medicine & Rehabilitation. We
are also thankful to Shaun Nanavati for his insights in using
ANSAR software, and to Dr. Joseph Colombo for the equip-
ment loan from ANSAR.
REFERENCES
Akselrod, S., Gordon, D. et al. (1981). Power spectrum analysis of
heart rate fluctuation: A quantitative probe of beat-to-beat cardio-
vascular control. Science, 213, 220-222.
doi:10.1126/science.6166045
ANSAR Medical Technologies (2005). The ANX version 3.0 autonomic
nervous system monitor user’s operations manual. ANSAR Medical
Technologies, Inc., 1-20.
Appelhans, B., & Luecken L. J. (2006). Heart rate variability as an
index of regulated emotional responding. Review of General Psy-
chology, 10, 229-240. doi:10.1037/1089-2680.10.3.229
Appelhans, B. M., & Luecken, L. J. (2008). Heart rate variability and
pain: Associations of two interrelated homeostatic processes. Bio-
logical Psychology, 77, 174-182.
doi:10.1016/j.biopsycho.2007.10.004
Aupperle, R. L., Allard, C. B. et al. (2012). Dorsolateral prefrontal cor-
tex activation during emotional anticipation and neuropsychological
performance in posttraumatic stress disorder. Archives of General
Psychiatry, 69, 360-371. doi:10.1001/archgenpsychiatry.2011.1539
Aysin, B., & Aysin, E. (2006). Effect of respiration in heart rate vari-
ability (HRV) analysis. Conference Proceedings—IEEE Engineering
in Medicine and Biology Society, 1 , 1776-1779.
doi:10.1109/IEMBS.2006.260773
Bal, E., Harden, E. et al. (2010). Emotion recognition in children with
autism spectrum disorders: Relations to eye gaze and autonomic state.
Journal of Autism and Developmental Disorders , 40, 358-370.
doi:10.1007/s10803-009-0884-3
Bazhenova, O. V., Plonskaia, O. et al. (2001). Vagal reactivity and af-
fective adjustment in infants during interaction challenges. Child De-
velopment, 72, 1314-1326. doi:10.1111/1467-8624.00350
Benarroch, E. E. (1993). The central autonomic network: Functional
organization, dysfunction, and perspective. Mayo Clinic Proceedings,
68, 988-1001. doi:10.1016/S0025-6196(12)62272-1
Berntson, G. G., Cacioppo, J. T. et al. (1991). Autonomic determinism:
The modes of autonomic control, the doctrine of autonomic space,
674

C. C. UY ET AL.
and the laws of autonomic constraint. Psychological Review, 98,
459-487. doi:10.1037/0033-295X.98.4.459
Bornhofen, C., & McDonald, S. (2008). Emotion perception deficits
following traumatic brain injury: A review of the evidence and ra-
tionale for intervention. Journal of the International Neuropsycholo-
gical Society, 14, 511-525. doi:10.1017/S1355617708080703
Colombo, J., Shoemaker, W. C. et al. (2008). Noninvasive monitoring
of the autonomic nervous system and hemodynamics of patients with
blunt and penetrating trauma. Journal of Trauma, 65, 1364-1373.
doi:10.1097/TA.0b013e31818cc307
de Sousa, A., McDonald, S. et al. (2012). Changes in emotional empa-
thy, affective responsivity, and behavior following severe traumatic
brain injury. Journal of Clinical and Experimental Neuropsychology,
34, 606-623. doi:10.1080/13803395.2012.667067
Fredrickson, B. L., & Levenson, R. W. (1998). Positive emotions speed
recovery from the cardiovascular sequelae of negative emotions.
Cognition & Emotion, 12, 191-220. doi:10.1080/026999398379718
Fredrickson, B. L., Mancuso, R. A. et al. (2000). The undoing effect of
positive emotions. Motivation and Emotion, 24, 237-258.
doi:10.1023/A:1010796329158
Gerlach, A. L., Wilhelm, F. H. et al. (2003). Embarrassment and social
phobia: The role of parasympathetic activation. Journal of Anxiety
Disorders, 17, 197-210. doi:10.1016/S0887-6185(02)00197-4
Giuliani, N. R., McRae, K. et al. (2008). The up- and down-regulation
of amusement: Experiential, behavioral, and autonomic consequences.
Emotion, 8, 714-719. doi:10.1037/a0013236
Gross, J. J., & Levenson, R. W. (1993). Emotional suppression: Physi-
ology, self-report, and expressive behavior. Journal of Personality
and Social Psychology, 64, 970-986.
doi:10.1037/0022-3514.64.6.970
Gross, J. J., & Levenson, R. W. (1997). Hiding feelings: The acute
effects of inhibiting negative and positive emotion. Journal of Ab-
normal Psychology, 106, 95-103. doi:10.1037/0021-843X.106.1.95
Hammond, F. M., Davis, C. S. et al. (2012). Relational dimension of
irritability following traumatic brain injury: A qualitative analysis.
Brain Injury, 26, 1287-1296. doi:10.3109/02699052.2012.706352
Healy, B. (2010). The effect of attentional control and heart-period
variability on negative affect and trait anxiety. Journal of General
Psychology, 137, 140-150. doi:10.1080/00221301003645079
Izard, C., Fine, S. et al. (2001). Emotion knowledge as a predictor of
social behavior and academic competence in children at risk. Psy-
chological Science, 12, 18-23. doi:10.1111/1467-9280.00304
Levenson, R. W., Ekman, P. et al. (1992). Emotion and autonomic ner-
vous system activity in the Minangkabau of west Sumatra. Journal of
Personality and Social P s y chology, 62, 972-988.
doi:10.1037/0022-3514.62.6.972
Mauss, I. B., Levenson, R. W. et al. (2005). The tie that binds? Coher-
ence among emotion experience, behavior, and physiology. Emotion,
5, 175-190. doi:10.1037/1528-3542.5.2.175
McDonald, S., Bornhofen, C. et al. (2009). Addressing deficits in emo-
tion recognition after severe traumatic brain injury: The role of fo-
cused attention and mimicry. Neuropsychological Rehabilitation, 19,
321-339. doi:10.1080/09602010802193989
Neumann, S. A., & Waldstein, S. R. (2001). Similar patterns of cardio-
vascular response during emotional activation as a function of affec-
tive valence and arousal and gender. Journal of Psychosomatic Re-
search, 50, 245-253. doi:10.1016/S0022-3999(01)00198-2
Porges, S. W. (1995). Cardiac vagal tone: A physiological index of
stress. Neuroscie n c e & Biobehavioral Re v iews, 19, 225-233.
doi:10.1016/0149-7634(94)00066-A
Porges, S. W. (1995). Orienting in a defensive world: Mammalian mo-
difications of our evolutionary heritage. A polyvagal theory. Psy-
chophysiology, 32, 301-318.
doi:10.1111/j.1469-8986.1995.tb01213.x
Porges, S. W. (2007). The polyvagal perspective. Biological Psychol-
ogy, 74, 116-143. doi:10.1016/j.biopsycho.2006.06.009
Pumprla, J., Howorka, K. et al. (2002). Functional assessment of heart
rate variability: Physiological basis and practical applications. Inter-
national Journal of Cardiology, 84, 1-14.
doi:10.1016/S0167-5273(02)00057-8
Rottenberg, J., Ray, R. D. et al. (2007). Emotion elicitation using film.
The handbook of motion elicitation and assessment. London: Oxford
University Press.
Sakuragi, S., Sugiyama, Y. et al. (2002). Effects of laughing and weep-
ing on mood and heart rate variability. Journal of Physiological An-
thropology and Applied Human Science, 21, 159-165.
doi:10.2114/jpa.21.159
Schaefer, A., Nils, F. et al. (2010). Assessing the effectiveness of a
large database of emotion-eliciting films: A new tool for emotion re-
searchers. Cognition & Emotion, 24, 1153-1172.
doi:10.1080/02699930903274322
Shiota, M. N., Neufeld, S. L. et al. (2011). Feeling good: Autonomic
nervous system responding in five positive emotions. Emotion, 11,
1368-1378. doi:10.1037/a0024278
Sternbach, R. A. (1962). Assessing differential autonomic patterns in
emotions. Journal of Psychosomatic Resea rc h, 6, 87-91.
doi:10.1016/0022-3999(62)90059-4
Stifter, C. A., Dollar, J. M. et al. (2011). Temperament and emotion
regulation: The role of autonomic nervous system reactivity. Devel-
opmental Psychobiology, 53, 266-279. doi:10.1002/dev.20519
Thurman, D. J., Alverson, C. et al. (1999). Traumatic brain injury in the
United States: A public health perspective. Journal of Head Trauma
Rehabilitation, 14, 602-615.
doi:10.1097/00001199-199912000-00009
Zuckerman, M., Klorman, R. et al. (1981). Facial, autonomic, and sub-
jective components of emotion: The facial feedback hypothesis ver-
sus externalizer-internalizer distinction. Journal of Personality and
Social Psychology, 41, 929-944. doi:10.1037/0022-3514.41.5.929